Test No. 114: Viscosity of Liquids

This Test Guideline describes methods to measure the viscosity of liquids. The methods listed are appropriate in principle for the investigation of Newtonian liquids. The measurement of non-Newtonian liquids is only possible with the rotational viscometer. Viscosity measurements are carried out predominantly according to five methods: the capillary viscometer, the flow cup, the rotational viscometer, the rolling ball viscometer and the drawing ball viscometer. Each determination of viscosity should preferably be made at a temperature of 20°C and at one other temperature approximately 20°C higher. At least two determinations should be made at each temperature. The evaluation of the viscosity measurement is to be carried out according to the standards in the case of capillary and forced ball viscometers. In the case of rotational viscometers, the specification of a viscosity is appropriate only for Newtonian fluids. For non- Newtonian fluids the results obtained are preferred in the form of flow curves which must be interpreted, assuming the validity of various laws of flow.